The present invention relates to a suspension system of a vehicle. A suspension system of a vehicle being considered, for the purposes of this disclosure, to be a group of components engaged to and supported by either the ground or one or more support structure(s) and also engaged to and supporting one or more suspended structure(s). Additionally, a suspension system of a vehicle comprises one or more spring(s) that support the weight of the suspended structure(s) engaged to the suspension system. The spring(s) of a suspension system of a vehicle support the weight of the one or more suspended structure(s) that are engaged to the suspension system in a cushioned manner by flexing and allowing the suspended structure to move relative to the support structure(s) or ground, which support the suspension system, when the vertical accelerations of the suspended structure and/or the support structure change and/or when the loading of the suspended structure is changed. For instance, when a load is dropped upon the suspended structure or when a vehicle in motion travels over uneven terrain, the springs of the suspension system flex and transmit forces between the suspended structure and the support structure or ground that are much less than the impact forces that would be transmitted between the suspended structure and the support structure or the ground if the suspended structure were supported by components of greater stiffness than the springs of the suspension system. By supporting the suspended structure in such a cushioned manner, the springs of a suspension system of a vehicle provide for more gentle support of the suspended structure and occupants or cargo supported thereby. Such gentle support can result in longer life of the suspended structure, decreased incidence of damage to cargo supported by the suspended structure, and increased comfort for occupants supported by the suspended structure.
Known suspension systems of vehicles utilize a number of different types of springs to support the weight of suspended structures. One common type of spring that is used in known suspension systems of vehicles to support the weight of suspended structures is a leaf spring. Leaf springs are elongated members that are used as a flexible beam to support the weight of a suspended structure. Each leaf spring of a suspension system of a vehicle has a plurality of mounting portions one or more of which is/are support mounting-portions that are engaged directly or indirectly to and directly or indirectly support at least a part of the weight of the suspended structure. One or more of the mounting portions of each of the leaf springs is/are supported mounting-portion(s) that is/are disposed at points distant from the one or more support mounting-portion(s) and that is/are engaged directly or indirectly to and are directly or indirectly supported by spring-support components. The spring-support components that a supported mounting-portion of a spring of a suspension system may be part of the support structure that supports the suspension system or may be part of the suspension system itself. The portions of each leaf spring that are disposed between each support mounting-portion and each supported mounting-portion function as a beam to support the loads applied at the support mounting-portion. When the loads at each support mounting-portion change, the magnitude of the bending of the portion of the leaf spring between that support mounting-portion and the nearest supported mounting-portion changes in proportion to the change in the load at the support mounting-portion. Leaf springs can be used in a suspension system of a vehicle to provide a simple, cost-effective, and easy to design suspension system as compared to suspension systems that include only springs of types other than leaf springs for supporting the weight of the suspended structure. A suspension system of a vehicle with leaf springs can provide such benefits because many designs of leaf springs are strong enough in all directions perpendicular to their longitudinal axis and also along their longitudinal axis to provide full location of the suspended structure they support without assistance from other structural components acting in parallel to them. In other words, in addition to providing full support for the suspended structure in vertical directions, leaf springs of a suspension system of a vehicle are capable of providing full support for the suspended structure in lateral and longitudinal directions. The use of only leaf springs in a vehicle""s suspension system to support the weight of the suspended structure does, however, have disadvantages as compared to the use of other types of springs for supporting the weight of the suspended structure. Leaf springs generally have greater weight than other types of springs with equivalent weight carrying capabilities. Due to a combination of factors which include weight carrying requirements, limitations in the length of leaf springs due to space constraints on a vehicle, and fatigue strength of the leaf springs, the use of leaf springs as opposed to other types of springs in a vehicle suspension system often requires greater spring rates of the leaf springs than would be necessary for other types of springs if employed. The greater spring rates that are often necessitated in a suspension system of a vehicle as a result of the use of leaf springs in lieu of other types of springs can result in a harsher ride for the occupants and cargo of the vehicle and reduced life of the suspended structure supported by the leaf springs. Additionally, many known designs of suspension systems of vehicles include leaf-spring packs, which include multiple leaf springs stacked upon one another to provide the requisite load carrying ability. One disadvantage of the use of such leaf-spring packs is that friction between each of the leaf springs and those positioned above and below it causes hysteresis in the reaction of the leaf-spring pack to changing loads. The hysteresis in leaf-spring packs results in the same negative consequences for suspension systems that utilize them as those negative consequences associated with increased spring rates.
Another type of spring that it is known to employ in suspension systems of vehicles to support suspended structures thereof is a pneumatic spring. Pneumatic springs comprise an expandable and contractable gas-compression chamber within which a gas, which is usually simply air, is compressed when the gas-compression chamber is contracted and within which the gas is expanded when the gas-compression chamber is expanded. Like leaf springs, pneumatic springs have two or more mounting portions. One or more of the mounting portions of a pneumatic spring of a suspension system of a vehicle is/are supported mounting-portions that are engaged directly or indirectly to and are supported directly or indirectly by spring-support components which may be components of the support structure that supports the suspension system or components of the suspension system itself. One or more of the mounting portions of a pneumatic spring of a suspension system of a vehicle is/are support mounting-portions that are engaged directly or indirectly to and support directly or indirectly the suspended structure that is supported by the suspension system. Gas pressure of the gas in the gas-compression chamber of a pneumatic spring directly or indirectly supports the support mounting-portions of the pneumatic spring. The components of a pneumatic spring that define its gas-compression chamber automatically move and/or elastically deform to positions and/or shapes that effect a volume of the gas-compression chamber at which the gas contained therein has a pressure that will just support the load applied to the support mounting-portion of the pneumatic spring. Pneumatic springs have little or no hysteresis, especially as compared to leaf-spring packs. Due to the relatively low hysteresis of pneumatic springs, the use of pneumatic springs in a suspension system of a vehicle generally provides for a more favorable ride than the use of leaf-spring packs, all other factors being equal. Most pneumatic springs that are traditionally used in suspension systems of vehicles, however, have the inherent disadvantage of being relatively weak in all modes of loading except for compression loading along axes between the support mounting-portion(s) and the supported mounting-portion(s) of the spring. For this reason, suspension systems of vehicles that utilize only pneumatic springs to support the weight of the suspended structure generally include relatively complex arrangements of linkages, which locate the suspended structure in those directions other than compression axes of the pneumatic springs thereof.
As a result, an object of the present invention is to provide a novel suspension-system for a vehicle, which novel suspension-system has relatively low hysteresis and which includes an arrangement of structural components of relatively little complexity for locating the suspended structure supported by the novel suspension-system.
The novel suspension-system for a vehicle of the present invention comprises one or more leaf springs and one or more pneumatic springs that act in parallel to one another to support the weight of a suspended structure supported by the novel suspension-system. The novel suspension-system of the present invention is constructed with the leaf springs thereof engaged to the other components of the vehicle in such a manner that they are capable of providing full lateral and longitudinal location of the suspended structure supported by the novel suspension-system. In most embodiments the leaf springs will, in fact, provide full lateral and longitudinal location of the suspended structure. Some constructions of a novel suspension system according to the present invention may, however, include components other than the leaf springs that are engaged to the suspended structure, without the inclusion of which in the novel suspension-system the leaf springs thereof would be fully capable of providing lateral and longitudinal location of the suspended structure, but which nonetheless do assist the leaf springs in providing lateral and longitudinal location of the suspended structure. The novel suspension-system of the present invention comprises two or more leaf-spring groups each of which comprises one or more leaf springs with its/their longitudinal axes disposed approximately horizontally. Each leaf-spring group comprises a primary leaf-spring. Each primary leaf-spring has two or more outer mounting-portions between which are disposed one or more inner mounting-portions. The outer mounting-portions of each primary leaf-spring are either both engaged directly or indirectly to the suspended structure or both engaged directly or indirectly to spring support component(s) that support the primary leaf-spring. Each of the inner mounting-portion(s) of a given primary leaf-spring is engaged directly or indirectly to whichever of the suspended structure and the spring-support components the outer mounting-portions are not engaged to. In other words, if the outer mounting-portions are engaged to the suspended structure the inner mounting-portion(s) is/are engaged to spring-support component(s) and if the outer mounting-portions are engaged to spring-support components the inner mounting-portion(s) is/are engaged to the suspended structure. One of the outer mounting-portions of each primary leaf-spring is an anchor portion of the primary leaf-spring. The anchor portion of each primary leaf-spring is engaged to either the suspended structure or a spring-support component in such a manner that, relative to whichever of the suspended structure and a spring-support component the anchor portion is engaged, translation of the anchor portion is prevented in all directions, rotation of the anchor portion about vertical axes is prevented, and rotation of the anchor portion about the longitudinal axis of the primary leaf-spring is prevented. The outer mounting-portion, of each primary leaf-spring, that is not an anchor portion is a reciprocating mounting-portion. The reciprocating mounting-portion of each primary leaf-spring is engaged to either the suspended structure or a spring-support component in such a manner that, relative to whichever of the suspended structure and a spring-support component the reciprocating mounting-portion is engaged to, translation of the reciprocating mounting-portion is prevented in all directions perpendicular to the longitudinal axis of the primary leaf-spring, rotation of the reciprocating mounting-portion about vertical axes is prevented, and rotation about the longitudinal axis of the primary leaf-spring is prevented. As a result of such engagements of the outer mounting-portions to either the suspended structure or spring-support components, each of the primary leaf-springs is prevented from moving relative to whichever of the suspended structure and the spring-support components the outer mounting-portions are engaged to with the exception of movement of portions of the primary leaf spring between the outer mounting portions when the primary leaf-spring deforms elastically. The inner mounting-portion(s) of each primary leaf-spring are engaged to either the suspended structure or one or more spring-support components in such a manner to rotationally and translationally fix the position of the inner mounting-portion(s) relative to whichever of the suspended structure and the spring-support components the inner mounting-portions are engaged to. As a result of this engagement of the inner mounting-portion(s) to the suspended structure or the spring-support component(s), movement of each of the primary leaf-springs relative to whichever of the suspended structure and the spring-support component(s) the inner mounting-portion(s) is/are mounted to is limited to movement of portions of the primary leaf-spring between the inner mounting-portion(s) and the outer mounting-portions when the primary leaf-spring deforms elastically. Thus, each of the two or more primary leaf-springs of the novel suspension-system is prevented from moving relative to both the suspended structure and the spring-support components with the exception of movement of portions of the primary leaf-spring relative to the suspended structure and the spring support components when the primary leaf-spring elastically deforms. Thus, the engagement of the primary leaf-springs of the novel suspension-system to the suspended structure and the spring-support components is such that the suspended structure and the spring-support components can only move relative to one another when the primary leaf-springs deform elastically. The primary leaf-springs of the novel suspension-system have sufficient tensile strength and resistance to buckling in directions parallel to their longitudinal axis and also have sufficient stiffness against bending within horizontal planes that they can transmit all lateral and longitudinal forces that are transmitted between the suspended structure and the spring-support components of the vehicle without the primary leaf-springs extending or buckling along their longitudinal axis or bending within horizontal planes. Thus, the primary leaf-springs of the novel suspension-system are capable of transmitting all horizontal forces between the suspended structure and the spring-support components without allowing any substantial relative horizontal movements between the suspended structure and the spring-support components. The stiffness against bending of the primary leaf-springs within vertical planes is, however, substantially less than their stiffness against bending within horizontal planes so that the primary leaf-springs can allow the intended controlled vertical movement of the suspended structure relative to the spring-support components.
In addition to leaf springs, the novel suspension-system of the vehicle of the present invention comprises one or more pneumatic springs which assist the leaf springs in vertically supporting the weight of the suspended structure of the vehicle. Each of the pneumatic springs of the novel suspension-system has a supported mounting-portion that is engaged directly or indirectly to one or more spring-support component(s) and a support mounting-portion that is engaged directly or indirectly to the suspended structure. The engagement of one or more of the pneumatic springs of the present invention to the suspended structure and the rest of the novel suspension-system is such that they act in parallel with the leaf-spring groups of the novel suspension-system to support the weight of the suspended structure. Because one or more of the pneumatic springs of the novel suspension-system act in parallel with the leaf-spring groups, and, thus, reduce the weight that must be supported by the leaf-spring groups, the leaf-spring groups may be constructed with a lower spring rate than would be necessary absent the pneumatic springs to assist the leaf-spring groups in supporting the suspended structure. For this reason, each of the leaf-spring groups of the novel suspension-system can be constructed with a lesser number of leaf springs, which reduces the hysteresis of the leaf-spring group and the novel suspension-system as a whole.
Thus, it can be seen that the above-mentioned object, as well as others not mentioned, have been met by the novel suspension-system for a vehicle of the present invention. The leaf-spring groups of the novel suspension-system function to laterally and longitudinally locate the suspended structure without the aid of complicated linkage assemblies. Further, as a result of the use of the pneumatic springs to assist the leaf-spring groups in supporting the suspended structure, the novel suspension-system of the present invention provides a less harsh ride than a traditional suspension-system that utilizes only leaf springs to support the weight of the suspended structure.